Additional targets of MicF have been defined and include regulation of Lrp expression in rich medium. A double negative feedback loop of MicF and Lrp regulation has been proposed [Holmqvist12].

The micF gene was originally found to encode a non-translated 174 nt antisense RNA that regulates OmpF abundance [Mizuno84]. It was later found that the primary transcript is a smaller, 93 nt RNA species [Andersen87]. The secondary structure of the MicF RNA has been examined [Schmidt95, Delihas97]. MicF is cleaved by RNase E in vitro [Schmidt95b] and may be destabilized by StpA [Deighan00] and is stabilized by Hfq [Urban07].

MicF was found in a ribonucleoprotein complex [Andersen90]; it was later determined that MicF binds Hfq [Zhang03i, Windbichler08] and that regulation of OmpF [Urban07] and Lrp [Holmqvist12] expression by MicF depends on the presence of Hfq. Regulation of OmpF does not depend on RNase E [Urban07].

Overexpression of micF from a high-copy-number plasmid causes reduced OmpF expression, compared to wild type, while expression of micF from a low-copy-number plasmid does not appear to affect OmpF expression [Matsuyama85, Aiba87]. Deletion of micF suppresses the OmpF-defective phenotype of a tolC mutant, probably by upregulating production of OmpF [Misra85, Misra87]. The defect in OmpC regulation exhibited by a micF mutant is suppressed by HrsA overproduction [Utsumi96].

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History:
Suzanne Paley on Thu Oct 21, 2004:
Position updated based on U00096.2 release of genome
Markus Krummenacker on Mon Oct 20, 1997:
The location of this gene on the E. Coli chromosome has not yet been determined.